Discovery of chemical messages between viruses could provide new way to induce HIV latency

27 January 2017

One of the first studies into viral communication shows that viruses that infect bacteria (phages) leave chemical messages for each other which help them decide whether to kill or linger. Disrupting these messages could provide a new way to control HIV.

A surprising new study has shown that phages speak to each other across an “elegant” communication network of molecules, leaving encoded information to be passed on to their later incarnations as they move and attack the cells of their host.

Scientists believe the findings could lead to new ways to disrupt viruses such as HIV and treat people living with the infection.

Experts have spoken of the importance of the discoveries, made at the Weizmann Institute of Science in Israel in the first study of its kind. They have named the protein which contains the communication after the Latin word arbitrium – meaning decision – because it helps the molecule to decide whether to kill the cell immediately or slip part of its genome inside it and stay dormant.

The study shows that increased levels of arbitrium stop phages killing bacteria and instead cause them to lie dormant in genomes. This is because they signal that they have destroyed large numbers of their host cells.

“It does make a lot of sense,” says Peter Fineran, a microbial geneticist at the University of Otago in New Zealand.

“If the phage is running out of hosts, it would try and limit its destruction, and sit quiet and wait for the host to re-establish growth.”

HIV injects its DNA into the material inside living CD4 cells, replicating itself and destroying them while causing a carrier’s CD4 count to fall rapidly.

HIV either prioritises its own reproduction, replicating many times, or remains dormant as an extra piece of DNA, ready to reactivate when triggered at a later stage. Whether an HIV infections is dormant or active might be controlled by a molecule similar to arbitrium.

“We were completely surprised to find the communication appearing from the phage,” says Professor Rotem Sorek, the microbial geneticist who led the investigation.

“We found it in hundreds of cases in nature. We don’t know yet if this kind of communication system is more broad or not.”

The communication process, known as quorum sensing, had only previously been seen in bacteria, which provided the original basis for the study.

Phages can see how many of their predecessors have carried out successful infections in previous cycles and estimate how many infections have taken place, helping them decide which method of attack to take.

Sorek suggests further studies should try to discover whether viruses which infect people can talk to each other, and says a molecule capable of driving HIV into complete latency would be “a good drug.”

“The virus that a virus spawns will be able to detect what its progenitors produce. They talk to each other in very specific languages. And, of course, it also opens the possibility that, if they talk about this one particular decision, they may talk about other things as well."